The archetypal Expressionist film is The Cabinet of Dr. Caligari (Germany, 1919), directed by Robert Wiene. A horror story involving sleepwalking, madness, murder, and sexual threat, the film is best known for its sets and scenery. Designed by the Expressionist Bauhaus art school, the sets are distorted, artificial, shadowy, and disorienting.
Expressionist elements (particularly sinister plots, horrific events, and chiaroscuro lighting, are found in German cinema throughout the 1920s and into the 1930s. Hitchcock was familiar with Expressionism from his time working in Germany in the 1920s as well as through his interest in modern art.

Nosferatu: A Symphony of Horror, a vampire movie directed by F. W. Murnau (1922).

The futuristic city in Fritz Lang's Metropolis (1927).
Lang's Metropolis: woman as temptress and as machine.

Expressionistic lighting and composition in Lang's Metropolis, above left, and M (1931).